Variable relay condenser



Patented oct. 7,1930

vU-Nrren s'rA'rvlez's` lLESTER L; IONESjsl 0F ORADELL, NEW JERSEY VARIABLE RELAY coNnENsEn. l

Application filed March 6,

This invention relates to a variable condenser and relates more particularly to acondenser which may be 7^ varied electrically as by i a change of circuit constants, and has specialreference to the provision of a variable condenser which maybe varied at a high rate of s ee l@In the radio art there is oftentimes required a, condenser whose capacity must be w varied at a rate which is sol high as to pre# clude the possibility of using mechanical l varying means-or a capacity which must be varied in a predetermined way. An example of such a requirement or desideratum occurs in the frequency' modulation of the carrier wave of a transmitting station, either for purf poses ofbroadcast transmission or for purposes of secrecy sending; and for such frequency modulation it is very desirable to em- 20 ploy a condenser which could be varied in a predetermined way and at a` high4 rate of speed forsecuring corresponding varlatlons 1n frequency.

The prime object of my presentl'nventlon centers about the provlsion of variable electrical condensers capable of being electrically varied at high speeds and in a predet termined Way, and thus capable ofbeingrused,

for. example, in frequency modulation and for the solution of other similar problems.

The invention utilizes certain inherent properties of an electron discharge relay tube; and is therefore termed by me a variable relay condenser, and by employing the principles ofthe present invention it is possible to secure `condensers substantially` free of losses, the capacities of which `may be varied at anyrate through a lar erange of values and at speedsv in excess-ofzmillions'of times per second. *l

The present application is a continuation l in part of my application for Letters Patent,

Serial No'. 742,342` filed October 8,1924 to Method of and means forfcontrollin ener feed' back in electron discharge devices. Patent No. 1,713,130, May 14,1929, the underlying principles'of electron discharge tube relays upon whichthe present invention isy based being disclosed in `said application -and in others of my copending applications such ,principles vbody invention may take.

192s. seal No. l25u9,452. as serial No. 42,399, filed July-e, 192,5 to

Electron discharge tube ampli er systems,

Patent No. 1,713,131, May 14, 1929, and Serial No. 198,061,1filed June 1l, 1927 to-Electron discharge t/ube amplier system, Patent N o. 1,673,287, June '12, 1928. I

i To the accomplishment of 4 the foregoing and such other objects as'will hereinafter appear, my inventionconsists in the elements and their relation one to the other, as hereina-fter more articularly described and sought to bede ned. in the claims, reference being had to the. accompanying drawings which show the preferred embodiment of my invention, and in which:l Fig. 1 is a wiring diagrammatic view showing one form of the relay condenser' of my invention,

Fig. 2 shows one of the applications of the same in the arts, the same being shown as used for obtaining frequencymodulation in transmitting systems. Iiig.v 3 is a graph explanatory of certain of the invention and the relation between lconstants used for certain elements of the circuits, and l Fig..4 is a wiring diagrammatic view showing another method of applying v the relay condenser of theinvention. The' relay condenser of my invention is based upon the properties ofthe electron discharge tube relay when organized -to emthe means for controlling orcompensating energy feed-back therein by a -feedforward action, as described and claimed in my aforesaid copendingapplication, Serial No. 742,342. These properties may.- be explained by reference to Fig. 1 of the'drawings which shows one form that my present The relay condenser, as shown in Fig. 1, comprises anelectron discharge tube a having 'a filament lcathods f, a grid g, an anode or plate p, a grid orinput circuit z', and a plate or output circuit o, the output circuit having an inductive load L '95 and a' resistance R related toproduce a given input capacity'in said tube which defines a condenser as represented'in the grid filament circuit by the phantom condenser K. This V Iinput capacity or condenser K is-,made vacharacteristics or values,

v `being poled `as shown in `ings.

riable by varying an electrical characteristic of said. relay, and more specifically, by modulating trodes of the relay. In the form of circuit o across the terminals 10, thereof, as indicated by the legend Modulating voltage.

The electrodes of the variable relay con-' denser may be supplied with suitable energy the ilament f being fed from an energy supply or batteryA A, the plate circuit 0 being provided with a B battery supply designated as B, and thc grid g being given a suitable vnegative bias as by means of the batteryC, these energy sources Fig. 1 of the draw- The out yut circuit o` may also lbe provided with a suitable radio frequency by-pass condenser 11. u 4

As is well known, the inductance L in theoutput or `plate circuit comprises a load impedance the grid plate tube capacity in my aforesaid copending applications,

which produces an energy feed-back through and as set forth rial Nos. 7 42,342 and 42,399,'a predetermined lvalue of Vresistance R 'in thev4 output circuit functions for producing an energy transfer or feed-.forwardfrom the input circuit v1 to the output-circuit `0 throughsaid grid plate tubecapacity and the relay action of the'tube, which'energy feed-forward may be made to compensate or neutralize the energy feedback. j This interrelation between the inductance load L and vtheresistance R produces a given augmented tube input capacity which isrepresentedby'tbe condenser K,

This resistance R is .preferably though not necessarily indu'ctancefree and is also preferably capacity-free lso-f that the resistance may be the decrease of platefvoltage due to the voltage drop in -the-plate jcircuit'and so that a balance for all frequencies may be had. The magnitude\of this resistance is generally ma e equal to the ratioA of the filament-plate to the amplification constant of Thus, with a filament-plate imthe tube.

pedance of 10,000 ohms and an amplification constant of 10,'the value of this 'resistance lRv should be about 1000 ohms. The values vof L and R' vary with the wave length range in which the condenser is used, 4and in the broadcast 'range the valueof L is preferably suchas to. give the plate circuit a natural wave length less than 200 meters. The resistance-should be high-'enough vt effect the desired control, butl should in practicebe -maintained at a minimum so as to prevent any appreciable voltage drop across the resistance, andtherefore any appreciable drop or reduction in the late voltage.

Viewed from t e standpoint of'the'energyv' relatlons in `the, interlinked or coupled input of, the Jresistance the energy supplied to one of the electhe in :A vention shown in Fig. 1, this is produced by a modulating voltage applied inthe output age, and this current is -forward capacity current kept as'. smallas possibleto minimize and output circuits of the tube, the insertion R in the plate circuit/ has the eiect of absorbing orabstracting energy from. the (grid correspon ng in variation with the energy circuit irlproportion to andv retransfer or feed-back that takes place from the plate circuit tothe grid circuit, Viewed Afrom the standpoint ofthe resistance relatlons of theinterlinkedcircuits' the resistance R in the platel circuit has Y a positive resistance 1n the-.grid orinput circuit i which may be made lto neutralize the the effect of introducing? negative resistance of the grid circuit result- 1n Tlgije abstraction of energy or the energy feedforward from the input circuit produced by the resistance in the plate circuit is 90 out of phase with the energy feed-back, but takes place in each ycycle so that the energy feedback is effectively compensated for or neutralized.

Thev effect of the inserted resistance in the l plate circuit of producing a feed-.forward of energy from the input circit to the output circuitin opposition to the 'energy feedbackl from` he output to the input circuit maybe explained onl vthe the'ory that the feed-forward capacity/ current -through the grid-plate capacity is 1n eiect magnified or augmented by Anitude oftheresistance'to nullify any part or the whole of the energy feed-back. This theory further explains the reason why the feed-'forward of energy always equalizes the from the feed-back of .energy thereto. l

the resistance in the plate cir' cuit due to the said resistance producing the preceding in-l the resistance in produc-.

feed-forward of lin series with the v feed-back of energy independent of any change inthe tube characteristics or constants, such equalization of the feed-forward -of energy with the feed-back of energy being due to the location of the resistance in the electronic current path. Thus with the resistance located in the output circuit, an increase in the filament current, which as known produces an increase in the feed-back of energy from the output to the input circuit due to an increase of the plate potential or the electronic flow of current in the output circuit, produces a. corresponding increasey in the potential drop -across the output resistance R, and hence a corresponding increase in the vplate voltage which is in phase with the grid voltage,

l.increase ofpabstraction orfeed-forward of resulting in an plate capacity of the tube resulting from replacement or t substitution of tubes of different types.

The effect on producing an agumented input capacity K by thus interrelating the in- Y ductance and resistance components L and R and the consequent possibility of applying this discovery to the production of variable .ondensers of my present invention will also be seen by`the following comparison. By inserting t e inductance L Vin the output cir- I cuit (Armstrong) the feed-back of energy is yof tuning of such an input Armstrong feed-back and l ates to feed exhibited or manifested by an increase in amplitude of the oscillation in an input c ircuit of the tube overwhat is caused by a signal in said input circuit, together with an' increase in the selectivity or sharpness of tuning of such an input circuit.. Correspondingly, but conversely, I have found that the introduction of substantially capacity and inductance free'resistance ofthe magnitude aforerelated in the plate circuit causes a reduction of the amplitude of oscillation in the input circuit below that which is due to, ak signal acting alone, together with a reduction of the selectivity or sharpness circuit. The comparing the my feed-forward is, in this respect, broadly similar but opposite. voltage operates through the grid-plate capacity to feed energy back to the input circuit. With my feed-forward resistance, the amplified-energy in the pla-te circuit operenergy forward through the grid-plate capacity. There is, however, this difference in the mechanics: In the Armstrong ed-back, substantially no change in the effective grid-plate capacity takes place, and the current which flows through the grid-plate capacit determining in art the energy feed-back, is measured by the gridplate capacity and plate voltage. In my mechanism of operation,

feed-forward system, on the other hand, the

effective grid-plate capacity is variable with the amplification of the system and the amount of feed-forward resistance in the plate circuit. y

It is this characteristic, therefore, of the capability of varying the input capacity K which I utilize for producing a variable relay condenser. The variation of this condenser K may therefore be obtained by varying the resistance R or any characteristic of the electrodes which ,would produce a variable amplification of the tube.y It is desirable, however, .to maintain the resistance R constant for the `reason that when the feed-forward 'pacities are plotted in mmfds.

In Armstrong the amplified plate` ing parts Aof Fig. 1 of the action of this resistanceis made to exactly compensate or neutralize for the feed-back actionl of the inductive vload L, the input circuit z' is devoid` of conductance, the negative resistance com onent due to the feedback being neutralized by the positive or damping resistance component, due to the feed-forward. The capacit or condenser K may therefore be obtaine asa pure condenser.

In Fig. 1 of the drawings I yshow means for obtaining the variations of the condenser K by modulating the voltage in the plate circuit. This is produced by applying the modulating voltage at the terminalslO, 10 of the plate or output circuit 0'. The effect of such a modulating voltage in the plate circuit is shown by the graph of Fig. 3 of the drawings wherein the plate volts are plotted as abscissae and the tube input caas ordinates. By reference to this graph itwill be seen that a modulated voltage over a range of 20 to 140 volts on the variation in tube input capacity from between 12 toL 30 mmfds. this being shown by `the curve J. By suitably selectingthe mean or-constant plate voltage supply, such as is indicated bythe dotted ordinate line at substantially volts, it is thus possible to secure variations of the input capacity K mil plate may produce a in accordance with the modulation energy supplied to the plate. I have found when theplate voltageis thus modulated that the input capacity of the condenser K may not only be made to change over the range shown in Fig. `3 of the drawings, but that such change may be effected with no perceptible deviation from the negligible input conductance.

In Fig. 2 of the drawings I show an application or use of such a variable relay condenser for securing frequency modulations in transmitter circuits, the variation of capacity being obtained by Avoltage variations in the grid or input circuit instead of in the plate or output circuit` of the electron tube relay; In this Fig. 2 of the drawings,the transmitter having the transmitter antenna 12 is provided with an oscillator 13, also designated by the legend Oscillator, the said oscillator having a grid circuit containing an inductance L. The relay condenser of the invention is applied to the inductance.

L for producing a variable capacity across a part or all of the inductance L', which capacity is represented by the phantom varia-v ble condenser `K produced by a condenser relay a embodying the principles of my invention. This relay a is provided with a grid circuit z", a plate circuit o', the plate circuithaving the inductance and resistance Vcom ponents L and R related in a manner similar to that described for the corresponddrawings, the

.'.55 multiplex or secrecy sending systems may glsobe used. In Fig. 3 of the drawings the i n spectively, these electrodes being supplred by relay a' being provided with 'the filament,

grid and plate electrodes f', g and p re- A, B and Q sources of energy, similar to that heretofore describedl for Fig. `1- of the drawings, poled as shown in Fig. 2 oft-he drawings. In the form of the invention here shown, one biasing battery C is used for both the oscillatorand the condenser tubes. If a higher biasing voltage is desired for lthe condenser tube a', a separate biasing battery may be'used therefor.

The oscillatory tube and condenser tube (a) are joined by tapping the lead con-v nected to the grid g along a point of the inductance L. The inductance L istapped at a suitable point to obtain a proper voltage on the rid of the condenser tube a. As shown,'t e inductance L .is tapped to swing the grid of the condenser tube to about v one-half of the grid swing of the oscillator tube. The point at whichthe inductance L is tapped also determines the capacity variations, the capacity variations obtainable increasing as the, tapped point is moved from the lower part of the coil L to the upper.

part thereof.` 'It will be apparent that the voltage applied to the grid g varies in a similar sense. If more voltage isapplied to the grid g', the grid bias and the modulating voltage for the condenser tube a should correspondingly be increased.

The modulating energy for the system shown in Fig. 2 of the drawings is obtained `by a modulation voltage supply in series with the grid circuit, as for example, by an audio amplifier 14- connected into the grid x circuitv of the tube a at the terminals 15, 15,

across which Aterminals a radio frequency by-pass condenser'l is placed. This form of the invention has the advantage that substantially no power is required to cause the variation of the relay condenser capacity;

curvel J shows the variation in the capacity of the condenser K- which is obtained by a modulation of the grid voltage between minus 2 and minus 14 volts,the mean or constant value of the grid voltage being taken at about 'minus 9 volts. With a relay condenser of this type and where approxi epimate'ly linear capacity variations with input voltage Avariations are desired, the normal voltage lon the grid would be held at about minus 9 volts, so as to hold the normal relay condenser capacity at itslapproximate midvalue.

Referring now to Fig. 4. of the drawings, I show another applicationV or use of the relay condenser of the invention wherein the condenser variations are effected by causing a' variation of electron emission, as for example by varyin the heater or filament current for the catho e. This methodof producing the condenser variations maybe applied to the stabilizing of the frequency of. an oscillator against slow variations of the -A battery voltage. In making this application, the input circuit 2 of the relay condenser tube a? having the filament, grid andl plate velectrodes f2, gzand p2 respectively isoconnected to the inductance coil La of the oscillator, as' shown in Fig. 4 of the drawings, and the output circuit' o2 of the condenser tube is provided with the inductance and resistance components L and R related in a manner similar to that heretoforedescribed. Both of the oscillator and relay condenser tubes are also supplied by the A, B and C sources of energy poled as shown in Fig. 4 of the drawings.

It has been found thatmost vacuum tube oscillator circuits such as shown in Fig. 4 of the drawings suffer changes in the frequency of the generated oscillations when the cathode heat is varied. Usually these changes are of a small order of magnitude, that is, 1% for normal battery voltage changes. This change is also usually an increase of generatedl frequency with de-` creasing cathode heat. The. relay condenser a2 is employed for compensating this change, and for accomplishing this the .relay tube (of the thoriated tungsten filament type) is operated at relatively high temperature so that an increase of temperature results in a reduction of electron emission. By connecting the lament f2 of the relay condenser tube a2 in' parallel with the loscillator cathode as shown inFig. 4 of the drawings, and by arranging the relay condenser in shunt with the oscillator condenser C? of the oscillator, the frequency compensation -desired can be effected. The variations produced in the relay condenser which are dependent upon-theheater or filament current arey necessarily restricted to slow variations on account of the time required to create temperature changes in the lament or cathode. -Where the type of oscillator is one in .which the frequency fallsas the cathode temperature falls the relay condenser may h ave its filament operated below the saturation point so that the emission and also the relay condenser value fall as the iilament temperature falls.

The use and-operation and the various api an electron discharge tube-relay pedance and the u the tube,

t and an output for producing corresponding will in the main be fully apparent from the above detailed description thereof. It ,will

be further apparent that While I have shown and described my invention in the preferred form, many changes and modifications may be made in the structure disclosed without departing from the spirit of the invention, defined in the following claims.

I claim:

1. A variable relay condenser comprising an electron discharge` tube relay including cathode,anode, and grid electrodes, an input or grid circuit comprising the condenser, and an output or anode vcircuit having inductance and resistance related to produce a given capacity in said condenser, and means for varying an electrical characteristic of said relay for producing predetermined variations in the capacity of said condenser.

2. A variable relay condenser comprising including cathode, anode, and gri'd electrodes, an inputl or grid circuit comprising the condenser, and an output or anode circuit having inductance and resistance related to produce for said condenser a given input capacity ofsubstantially no conductance in said tube, and means for varying an electrical characteristic of said relay for producing predetermined variations in the capacity of said condenser.

3. A variable relay condenser comprising ,an electron discharge tube relay including cathode, plate, and gridelectrodes, an input or grid circuit comprising vthe condenser,

or plate circuitn having inductance and resistance related to produce a given augmented capacity in said condenser, said resistance having-a magnitude ofthe order of the ratio of'the plate iinamplification constant of and means for varying an electrical characteristic of said relay for producing variations in the capacity of said condenser.

4.l A variable relay condenser comprising an electron discharge tube relay including cathode, anode, and grid electrodes, an input or grid circuit comprising the condenser, and an output or anode circuit having inductance and resistance related to produce a given input capacity in said condenser, and a modulating means for electrically varying at a high rate a characteristicof said relay high speed va-V nations in the ,capacityl of said condenser.

5. A variable relaycondenser comprising an electron discharge tube relay including cathode, plate, and grid electrodes, an input or grid circuit comprising the condenser, and an output or plate circuit having 'inductance and resistance related to produce a given augmented capacity in said condenser, and means for predeterminedly varyingthe grid-plate current How through said relay for producing variations in the capacity of said condenser.

6. A variable' relay condenser comprising an electron discharge tube relay having cathode, plate and grid electrodes, a grid or input circult comprising the condenser, and a plate or output circuit' coupled to the grid circuit through the grid-plate capacity of the tube, an inductive load in said output circuit for producing an energy feedback through the gridplate tube capacity, resistance in said output circuit for producing a predetermined ener transfer or feed-forward from the inputclrcuit to the output circuit through said gridplate tube capacity and through the relay action of the tube forcompensatingI for said energy feedback, said inductive'load and revsistance .producing a given capacity in said condenser, and means for varying an electrical characteristic ofsaid rela for producing predetermined variations o the capacity in said condenser. 4

7. A variable relay condenser comprising an electron discharge tube relay having cathode, plate, andgrid electrodes, a grid or input circuit comprising the condenser, and a plate or output circuit coupled to the grid circuit through the grid-plate capacity of the tube, an inductive load-in said output circuit for producing an energy feedbackthrough the grid plate tube. capacity, resistance in sald output circuit for producing a predetermined energytransfer or feed-forward from the input circuit to the output circuit through sald grid-plate tube capacity and through the relay action of the tubefor substantially neutralizing said energy feedback, said inductive loadand resistance producing for said condenser a given input capacity of substantially no conductance in said tube, and a modulating means for varying at a high speed an elecsaid relay for varying the capacity of said` condenser.

9. A variable relay condenser comprising an electron discharge tube relay having cathode, plate, and grid electrodes,a grid or input circuit comprising the condenser, and a plate or output circuit coupled to the .grid circuit through the grid plate capacity of the tube,

an inductive load in said output circuit for producmgan energy feedback through kthe grid-plate tube capacity, resistance in said output circuit for producing a predeterminedv relay for producenergy transfer or feed-forward fro'in the ini 4 put circuit to the output circuit through said resistance producing a condenser,

ay action of the tubefor compensatin rid-plate tube capacity and through the reor feedback, said inducti-(ve loa and given capacity in said to apply a modulation `said energy and means voltagebetweentwo of the electrodes of said relay to cause a variation of the capacity of m' said condenser.

v an electron dischargeY` tube relay including /one of the circuits of said condenser.

12. A variable relay condenser comprising.

cathode, plate, and grid electrodes, an input or grid Vcircuit comprising the condenser, and an output orplate circuit having inductance and' resistance related to produce a given capacity. in 'said condenser over a given fre- ,quenc' band, means for supplying energy to `one`o said circuitsof the relay,`and a means for ,modulating the for varying the capacity an electron discharge tube relay including cathode, plate., and grid electrodes, an input or grid circuit comprising the condenser, and an output or plate circuit having inductance and resistance related to produce a given augmented capacity in'said condenser over a given frequency band, one of the circuits eing. supplied with a mean voltage, and means to apply a varying modulationc voltage to said last mentioned circuit for varying the capacity of said condenser in a predetermined way.

lation com rising an oscillator circuit the ,oscillation requency of which is atleast partially dependent upon the capacitance of a portion of said circuit, and a variable relay condenser for determining the said capacitance, said relay condenser comprising an electron ldischarge tube 'relay including cathode, anode, and grid electrodes, a gri circuit comprising the said condenser, and ananode circuit having inductance and resistance related to produce a lven capacitance in said condenser, means or supplying energy to one of said relay circuits, and means for modulating the energy in-order to vary the capacitance of said condenser and the frequency of said oscillator.

14. An arrangement for frequency modulation comprising an oscillator .circuit the lation potential between 13. An arrangement for frequency moduoscillation frequency of which is at least partially dependent upon the capacitance of a portion of said circuit, and a variable relay condenser for determining the said capacitance, said relay condenser comprising van electron discharge tube relay includin cathode, anode, and grid electrodes, a gri circuit comprising the said condenser, and an anode circuit havi ance related to pro uce a giveny capacitance in said condenser, and means to apply a modutwo of the electrodes of said relay in order to vary the capacitance of said condenser and the frequency of said oscillator.

Signed at New York, in the county of New York and State of New York, 'this 3rd day of March, A vD. 1928.

` LESTER L. JONES.

for varying the ca- 1 energy supplied to said linductance and resist- 

